A type of silicon detector known as AXUV (absolute extreme ultraviolet) photodiodesis successfully used to measure the radiated power in EAST.The detector is characterizedby compact structure,fast temporal response (<0.5 s) and flat spectral sensitivity in the rangefrom ultra-violet to X-ray.Two 16-channel AXUV arrays are installed in EAST to view the wholepoloidal cross-section of plasma.Based on the diagnostic system,typical radiation distributionsfor both limiter and divertor plasma are obtained and compared.As divertor detachment occurs,the radiation distribution in X-point region is observed to vary distinctly.The total radiationpower losses in discharges with different plasma parameters are briefly analyzed.
In this paper,the singular value decomposition(SVD) method as a filter is applied before the tomographic inversion of soft-X-ray emission.Series of ’filtered’ signals including specific chronos and topos are obtained.(Here,chronos and topos are the decomposed spatial vectors and the decomposed temporal vectors,respectively).Given specific magnetic flux function with coupling m = 1 and m = 2 modes,the line-integrated soft-X-ray signals at all chords have been obtained.Then m = 1 and m = 2 modes have been identified by tomography of simulated ’filtered’ signals extracted by the SVD method.Finaly,using the experimental line-integrated soft-X-ray signals,m = 2 competent mode of complex magnetohydrodynamics(MHD) activities during internal soft disruption is observed.This result demonstrates that m = 2 mode plays an important role in internal disruption(Here,m is the poloidal mode number).
A compound sawtooth with an incomplete relaxation was observed in EAST's lower hybrid current drive(LHCD)plasma. The sub-crash phase of the compound sawtooth corresponds to a longer-lasting and slower-growing 1/1 mode.Based on the two-dimensional(2D) SXR tomography, the time-dependent 2D image of a compound sawtooth crash is obtained. The island produced during a resistive internal kink mode is observed in the all crash phases of the compound sawtooth. The destabilization of 1/1 long-lasting saturated 1/1 mode is related to the current driven by the LHCD near the q = 1 surface.
